The present invention relates to a system for the excavation of dirt, water or other material from an excavation site through the use of a vacuum to draw material into a spoils tank, and through the use of a pneumatic or hydraulic system to agitate spoils in the tank so that solids are suspended for convenient evacuation of the tank. The use of vacuum excavation as a means for the removal of dirt, water, or other material from an excavation site, or in the handling of liquid waste streams (manure, etc.) is known and has been practiced in the prior art. Vacuum excavation is widely considered to be superior to traditional excavation techniques such as manual or mechanical digging. Vacuum excavation typically involves the use of a vacuum system to pull a slurry or debris stream that may exist or that may be created by the use of compressed air, high pressure water, or other mediums capable of loosening hard-packed material.
Important applications for vacuum excavation systems include environmental cleanup, the collection of the slurry created in the process of directional drilling or the xe2x80x9cpot-holingxe2x80x9d of utilities. xe2x80x9cPot-holingxe2x80x9d refers to the excavation of a hole to access or view utilities. Pot-holing is preferred over prior art techniques such as digging with shovels, backhoes, etc., which often results in damage to the utilities and a corresponding demand for expensive repair and reconstruction. Depending on the utility, such damage may present danger to workers or nearby residents in addition to increased costs necessarily associated with repair and increased labor costs associated with digging. When the vacuum excavation of a slurry is utilized for pot-holing, access is possible without risk of damage to the utilities. In addition, when the vacuum excavation is coupled with radar or other utility locating techniques, the amount of excavation required may be minimized.
Prior art vacuum excavation systems, include those disclosed in U.S. Pat. No. 5,016,717 (1991, Simmons et. al., the xe2x80x9c""717 patentxe2x80x9d) and U.S. Pat. No. 5,295,317 (1994, Perrott, the xe2x80x9c""317 patentxe2x80x9d). The ""717 patent discloses a vehicle mounted vacuum excavation system having a tank mounted on a lift mechanism to facilitate the raising and tilting of the tank to release excavated materials by dumping through an openable rear hatch or end wall of the tank. The invention of the ""717 patent allows for the settling of solids at a bottom region of the tank and provides for the addition of a vibrator to prevent compaction of particles and to facilitate release when the tank is tilted for dumping.
The ""317 patent discloses a mobile vacuum excavation system and tank that features a slurry water recovery system to reuse excavation water. The ""317 patent discloses a screen assembly and a dual chambered water tank to allow the use of recovered slurry water from a first chamber, supplemented with make-up water from the supplementary chamber. Therefore, the invention of the ""317 patent seeks to minimize the retention of excavation materials by separating excavated solids from retrieved water and minimizing water usage associated with slurry creation. Although the reuse of slurry water in the invention of the ""317 patent decreases the downtime required for tank evacuation and the environmental concerns associated with the dumping of excavated material, the ""317 patent does not disclose an improved method for tank agitation and materials release.
It is therefore an object of the present invention to provide a system for the vacuum excavation of materials that allows the convenient suspension of solids in the slurry or spoils tank and allows evacuation of the tank without the need for a tilt mechanism or the need for an end wall adapted for dumping.
It is a further object of the present invention to provide such a system wherein air or other fluid delivered through a manifold system to the slurry or spoils tank provides agitation to the slurry.
It is a further object of the present invention to provide such a system wherein a separate engine is employed to power a fluid pump to deliver water or other materials-loosening fluid to an excavation site to aid in the creation of a slurry.
It is a further object of the present invention to provide a pump and conduit system whereby vacuum generation in the tank and agitation or pressurization of the tank may be controlled through an air mover and valve assembly to consolidate the vacuum and pressurization functions to an air mover.
The present invention utilizes pneumatic or hydraulic agitation of a spoils tank to suspend vacuum-excavated materials for release thus facilitating the efficient emptying of the slurry tank via a controlled gravity and/or pressure-driven evacuation of the tank rather than dumping. Such an arrangement eliminates the need for hydraulic lifts and an openable tank end wall. Further, release through a port or line rather than dumping allows for greater control during evacuation of the tank, which control may be important in applications involving contaminated spoils.
A mobile base is provided upon which a spoils tank and air mover are provided. A fluid source such as a water tank and water pump may be provided, although, depending upon the location of the excavation site, external water sources may be available to provide a loosening agent. Manifolds within the spoils tank provide for the injection of air into the excavated material in the tank to cause or maintain suspension. Preferably, separate engines are utilized to power a vacuum pump and a water pump to prevent excessive wear and to prevent the xe2x80x9cpulling downxe2x80x9d that can occur when only one engine is used. However, one engine may be utilized if that engine will provide sufficient power to drive both pumps. In addition, the preferred air mover in the present invention comprises a rotary vane pump to create a deeper vacuum than traditional blowers or alternative pumps, which typically are less capable of tolerating the foreign materials inherent in excavation applications.